1. Field of the Invention
The present invention relates to an imaging apparatus including a cyclic noise reduction circuit.
2. Description of the Related Art
A cyclic noise reduction circuit is a circuit for reducing noise of a moving image signal of a digital video camera or the like. This circuit uses a signal of the same pixel obtained for each frame to reduce the noise.
When a cyclic coefficient of the cyclic noise reduction circuit is determined, it is necessary to be determined in consideration of both a noise component and the amount of tailing of a signal in the previous frame. In Japanese Patent Application Laid-Open No. 2000-278592, a method is discussed in which a cyclic coefficient is changed corresponding to zooming, thereby reducing tailing during zooming. Further, in Japanese Patent Application Laid-Open No. 7-162718, a method is discussed in which movement of an object is detected in order to change a cyclic coefficient in an area where movement is present, thereby reducing tailing.
When various types of parameters concerning an imaging by an imaging system or a signal processing by a signal processing system are changed, such as a change of angle of view by zooming and a change of contrast, a signal to be input to a noise reduction circuit may be changed, and a cyclic coefficient suitable for the state after the change may be changed from that before the change. At this time, if the cyclic coefficient suitable for the state after the change of parameter is simply set and changed, an image effect that causes discomfort for a user may occur when the parameter is changed.
For example, when the change of parameter is executed in the signal processing system and a color is changed, the color may be rapidly changed or gradually changed depending on a cyclic coefficient after the change. Further, when the parameter change is executed in the imaging system and an angle of view is changed by magnifying an image to be output, the image may be changed to an image rapidly or gradually follows the change in angle of view depending on a cyclic coefficient after the change.
A difference in change of image when a parameter is changed by these cyclic coefficients may result in an uncomfortable image effect according to a use environment or a request of a user. When the user does not intend to output an unnatural image to the eye on a display screen, such as a live view, it may be undesired that the color or the angle of view is rapidly changed by the cyclic coefficient after the change.
On the contrary, for example, when the user intends to confirm an effect on an image by the change of various types of parameters in succession, it may be undesired that the image is gradually changed by the cyclic coefficient after the change.